Handling scheduling request collisions with an ack/nack repetition signal

ABSTRACT

Systems and methods for handling of scheduling request collisions with an ACK/NACK repetition signal are provided. A pending scheduling request may be refrained from being transmitted due to the collision. The SR counter may be refrained from incrementing and the SR prohibit timer may be refrained from starting such that additional latency is not introduced into the scheduling request procedure. Alternatively, a pending scheduling request may be transmitted with the ACK/NACK repetition signal in the same subframe when the collision occurs. The ACK/NACK repetition signal may be transmitted on the SR PUCCH resource to indicate a positive scheduling request. If there is no pending scheduling request to be transmitted, the ACK/NACK repetition signal may be transmitted on the ACK/NACK PUCCH resource.

CLAIM OF PRIORITY

This application claims priority to U.S. patent application Ser. No.13/417,978, filed on Mar. 12, 2012, the entire contents of which arehereby incorporated by reference.

FIELD

This disclosure relates to communication networks and, moreparticularly, to handling scheduling request collisions with anacknowledgement/negative acknowledgement (ACK/NACK) repetition signal.

BACKGROUND

In an evolved universal terrestrial radio access network (E-UTRAN), userequipment (UE) may request uplink resources for uplink data transmissionby transmitting a scheduling request (SR) to a serving evolved Node B(eNB). The eNB may then provide a physical uplink shared channel (PUSCH)grant to the UE for uplink data transmission if uplink resources areavailable. A physical layer ACK/NACK transmission provides feedbackinformation to the eNB regarding whether a transmitted downlinktransport block on the physical downlink shared channel (PDSCH) issuccessfully received or not. An ACK/NACK signal may be repeatedlytransmitted in consecutive uplink subframes to allow better receptionquality at the eNB.

DESCRIPTION OF DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic representation of an example wireless cellularcommunication system.

FIG. 2 is a schematic block diagram illustrating various layers of anaccess node and user equipment in a wireless communication network.

FIG. 3 is a schematic block diagram illustrating an access node device.

FIG. 4 is a schematic block diagram illustrating a user equipmentdevice.

FIG. 5A is a schematic block diagram illustrating an uplink hybridautomatic repeat request (HARQ) entity in user equipment.

FIG. 5B is a schematic block diagram illustrating an uplink HARQ processmodule in user equipment.

FIG. 6 is a flow chart illustrating an example method for handling ascheduling request collision with an ACK/NACK repetition signal using amedium access control (MAC) layer of user equipment.

FIG. 7 is a process flow chart illustrating an alternative method forhandling a scheduling request collision with an ACK/NACK repetitionsignal using a physical layer of user equipment.

DETAILED DESCRIPTION

The present disclosure is directed to systems and methods for handlingcollisions between scheduling request (SR) transmissions and ACK/NACKrepetition signals. In some implementations, an SR transmissioncollision occurs when a UE is configured to transmit an ACK/NACKrepetition signal and a pending SR in the same subframe. In someimplementations, an ACK/NACK repetition signal includes an ACK/NACKsignal which is part of an ACK/NACK repetition sequence. The ACK/NACKsignal may be repeated multiple times in consecutive uplink subframe inan ACK/NACK repetition sequence when ACK/NACK repetition is configuredin the UE. To address these types of collisions, the UE can, in someimplementations, execute one or more of the following: (1) handle the SRcollisions with an ACK/NACK repetition signal in the same manner as foran SR collision with a measurement gap, i.e., the UE may refrain fromincrementing an SR counter and refrain from starting an SR prohibittimer; or (2) transmit a positive SR simultaneously with an ACK/NACKrepetition signal when ACK/NACK repetition is configured using the sameapproach as for the case when ACK/NACK repetition is not configured. Inthe first implementation, the UE may refrain from transmitting thepending SR when there is a collision with an ACK/NACK repetition signal.In addition to refraining from transmitting the pending SR, the UE mayalso refrain from incrementing the SR counter and refrain from startingthe SR prohibit timer. The SR counter may count or otherwise track thenumber of transmitted SRs by the UE. The SR prohibit timer may preventthe pending SR from being transmitted before the SR prohibit timerexpires. By refraining from incrementing the SR counter, the UE maystill perform a maximum number of SR transmissions configured by anevolved Node B (eNB) serving the UE, which may optimize, maximize orotherwise increase the chance of success for the scheduling requestprocedure. By refraining from starting the SR prohibit timer, additionallatency may be avoided when opportunities for SR transmissions occur ata later instance because the UE need not wait until the SR prohibittimer expires before transmitting the pending SR.

In the second implementation, the UE may transmit the pending SR andACK/NACK repetition signal simultaneously when the collision occurs. Apositive SR may be communicated to the eNB by transmitting the ACK/NACKrepetition signal on the SR physical uplink control channel (PUCCH)resources rather than on ACK/NACK PUCCH resources. The eNB may detectthe positive SR message when an ACK/NACK signal is received on the SRPUCCH resources. By transmitting the SR and ACK/NACK repetition signalsubstantially simultaneously or otherwise concurrently, the UE mayobtain an uplink resource allocation relatively quickly by avoiding arandom process procedure in order to obtain uplink transmissionresources. Therefore, additional latency may not be introduced into thescheduling request procedure and subsequent assignment of an uplinkgrant by the eNB. Furthermore, the probability of the UE falling back toa random access procedure in order to obtain uplink transmissionresources may be reduced.

FIG. 1 is a schematic representation of an example wireless cellularcommunication system 100 based on the third generation partnershipproject (3GPP) LTE, also known as Evolved Universal Terrestrial RadioAccess (E-UTRA). The cellular network system 100 shown in FIG. 1includes a plurality of base stations 112 a and 112 b. In the LTEexample of FIG. 1, the base stations are shown as evolved Node Bs (eNBs)112 a and 112 b. It will be understood that the base station may operatein any mobile environment, including macro cell, femto cell, pico cell,or the base station may operate as a node that can relay signals forother mobile and/or base stations. The example LTE telecommunicationsenvironment 100 of FIG. 1 may include one or more radio access networks110, core networks (CNs) 120, and external networks 130. In certainimplementations, the radio access networks may be E-UTRANs. In addition,in certain instances, core networks 120 may be evolved packet cores(EPCs). Further, there may be one or more mobile electronic devices 102a, 102 b operating within the LTE system 100. In some implementations,2G/3G systems 140, e.g., Global System for Mobile communication (GSM),Interim Standard 95 (IS-95), Universal Mobile Telecommunications System(UMTS) and CDMA2000 (Code Division Multiple Access) may also beintegrated into the LTE telecommunication system 100.

In the example LTE system shown in FIG. 1, the EUTRAN 110 includes eNB112 a and eNB 112 b. Cell 114 a is the service area of eNB 112 a andCell 114 b is the service area of eNB 112 b. UEs 102 a and 102 b operatein Cell 114 a and are served by eNB 112 a. The EUTRAN 110 can includeone or more eNBs (i.e. eNB 112 a, eNB 112 b) and one or more UEs (i.e.,UE 102 a and UE 102 b) can operate in a cell. The eNBs 112 a and 112 bcommunicate directly to the UEs 102 a and 102 b. In someimplementations, the eNB 112 a or 112 b may be in a one-to-manyrelationship with the UEs 102 a and 102 b, e.g., eNB 112 a in theexample LTE system 100 can serve multiple UEs (i.e., UE 102 a and UE 102b) within its coverage area Cell 114 a, but each of UE 102 a and UE 102b may be connected only to one eNB 112 a at a time. In someimplementations, the eNBs 112 a and 112 b may be in a many-to-manyrelationship with the UEs, e.g., UE 102 a and UE 102 b can be connectedto eNB 112 a and eNB 112 b. The eNB 112 a may be connected to eNB 112 bwith which handover may be conducted if one or both of the UEs 102 a andUE 102 b travels from cell 114 a to cell 114 b. The UEs 102 a and 102 bmay be any wireless electronic device used by an end-user tocommunicate, for example, within the LTE system 100. The UE 102 a or 102b may be referred to as mobile electronic device, user device, mobilestation, subscriber station, or wireless terminal. The UE 102 a or 102 bmay be a cellular phone, personal data assistant (PDA), smart phone,laptop, tablet personal computer (PC), pager, portable computer, orother wireless communications device.

The UEs 102 a and 102 b may transmit voice, video, multimedia, text, webcontent and/or any other user/client-specific content. On the one hand,the transmission of some of these contents, e.g., video and web content,may include high channel throughput to satisfy the end-user demand. Onthe other hand, the channel between UEs 102 a, 102 b and eNBs 112 may becontaminated by multipath fading, due to the multiple signal pathsarising from many reflections in the wireless environment. Accordingly,the UEs' transmission may adapt to the wireless environment. In short,the UEs 102 a and 102 b generate requests, send responses or otherwisecommunicate in different means with Enhanced Packet Core (EPC) 120and/or Internet Protocol (IP) networks 130 through one or more eNBs 112.In this disclosure, the UEs 102 a and 102 b may receive a PUCCH resourceassignment for the SR (e.g., the SR PUCCH resource index, SR periodicityand subframe offset) and ACK/NACK repetition signal (e.g. the ACK/NACKPUCCH resource index, the ACK/NACK repetition factor) from the eNBs 112.The UEs 102 a and 102 b may subsequently transmit SRs and ACK/NACKrepetition signals using the PUCCH resources assigned by the eNBs 112.Further, the UEs 102 a and 102 b may receive an RRC message from theeNBs 112 indicating the SR prohibit timer value and the maximum numberof SR transmissions. In some implementations, the UEs 102 a and 102 bmay determine that a pending SR transmission collides with an ACK/NACKrepetition signal, and thereby refrain from transmitting the pending SRtransmission. In addition, the UEs 102 a and 102 b may refrain fromincrementing the SR counter and refrain from starting the SR prohibittimer in order to optimize, maximize or otherwise increase the chance ofsuccess for the SR procedure. In some implementations, the UEs 102 a and102 b may determine that a pending SR transmission collides with anACK/NACK repetition signal, and transmit the pending SR and the ACK/NACKrepetition signal in the same subframe. Instead of transmitting theACK/NACK repetition signal on the ACK/NACK PUCCH resource, the UEs 102 aand 102 b may transmit the ACK/NACK repetition signal on the SR PUCCHresource such that both a positive SR request and the ACK/NACKrepetition signal are communicated to the eNBs 112 in the same subframe.

A radio access network is part of a mobile telecommunication systemwhich implements a radio access technology, such as UMTS, CDMA2000 and3GPP LTE. In many applications, the Radio Access Network (RAN) includedin a LTE telecommunications system 100 is called an EUTRAN 110. TheEUTRAN 110 can be located between UEs 102 a, 102 b and EPC 120. TheEUTRAN 110 includes at least one eNB 112. The eNB can be a radio basestation that may control all or at least some radio related functions ina fixed part of the system. The at least one eNB 112 can provide radiointerface within their coverage area or a cell for UEs 102 a, 102 b tocommunicate. The eNBs 112 may be distributed throughout the cellularnetwork to provide a wide area of coverage. The eNB 112 directlycommunicates to one or more UEs 102 a and 102 b, other eNBs, and the EPC120. In this disclosure, the eNBs 112 may configure an SR PUCCH resourceand an ACK/NACK repetition signal PUCCH resource for the UEs 102 a and102 b. The eNBs 112 may decode the SRs and ACK/NACK repetition signalsfrom the UEs 102 a and 102 b on the assigned PUCCH resource. A positiveSR may be detected at the eNBs 112 when there is a presence of signal onthe assigned SR PUCCH resource for the UEs 102 a and 102 b. The ACK/NACKrepetition signal may be decoded on the ACK/NACK PUCCH resource. In someimplementations, the eNBs 112 may decode the ACK/NACK repetition signalon the SR PUCCH resource when the pending SR transmission collides withthe ACK/NACK repetition signal for UEs 102 a and 102 b. The eNBs 112 maydetermine that SRs from the UEs 102 a and 102 b are received in the samesubframe as the ACK/NACK repetition signals.

The eNB 112 may be the end point of the radio protocols towards the UEs102 a, 102 b and may relay signals between the radio connection and theconnectivity towards the EPC 120. In certain implementations, the EPC120 is the main component of a core network (CN). The CN can be abackbone network, which may be a central part of the telecommunicationssystem. The EPC 120 can include a mobility management entity (MME), aserving gateway (SGW), and a packet data network gateway (PGW). The MMEmay be the main control element in the EPC 120 responsible for thefunctionalities comprising the control plane functions related tosubscriber and session management. The SGW can serve as a local mobilityanchor, such that the packets are routed through this point for intraEUTRAN 110 mobility and mobility with other legacy 2G/3G systems 140.The SGW functions may include the user plane tunnel management andswitching. The PGW may provide connectivity to the services domaincomprising external networks 130, such as the IP networks. The UE 102,EUTRAN 110, and EPC 120 are sometimes referred to as the evolved packetsystem (EPS).

Though described in terms of FIG. 1, the present disclosure is notlimited to such an environment. In general, cellular telecommunicationsystems may be described as cellular networks made up of a number ofradio cells, or cells that are each served by a base station or otherfixed transceiver. The cells are used to cover different areas in orderto provide radio coverage over an area. Example cellulartelecommunication systems include Global System for Mobile Communication(GSM) protocols, Universal Mobile Telecommunications System (UMTS), 3GPPLong Term Evolution (LTE), and others. In addition to cellulartelecommunication systems, wireless broadband communication systems mayalso be suitable for the various implementations described in thepresent disclosure. Example wireless broadband communication systemsinclude IEEE 802.11 wireless local area network, IEEE 802.16 WiMAXnetwork, etc.

FIG. 2 is a schematic block diagram 200 illustrating various layers ofan access node and user equipment in a wireless communication networkaccording to one implementation. The illustrated system 200 includes aUE 205 and an eNB 215. The eNB can be referred to as a “network,”“network component,” “network element,” “access node,” or “accessdevice.” FIG. 2 shows only these two devices (alternatively, referred toas “apparatuses” or “entities”) for illustrative purposes, and a skilledartisan may appreciate that the system 200 can further include one ormore of such devices, depending on the implementations. The eNB 215 cancommunicate wirelessly with the UE 205.

Each of the devices 205 and 215 includes a protocol stack forcommunications with other devices via wireless and/or wired connection.The UE 205 can include a physical (PHY) layer 202, a medium accesscontrol (MAC) layer 204, a radio link control (RLC) layer 206, a packetdata convergence protocol (PDCP) layer 208, a radio resource control(RRC) layer 210, and a non-access stratum (NAS) layer 212. The UE 205may also include one or more antennas 214 coupled to the PHY layer 202.In the illustrated implementation, a “PHY layer” can also be referred toas “layer 1.” The other layers (MAC layer, RLC layer, PDCP layer, RRClayer and above) can be collectively referred to as a “higher layer(s).”The SRs and ACK/NACK repetition signals described in this disclosure maybe transmitted by the physical layer 202 of the UE 205. The SR counter,SR prohibit timer, and HARQ processes (described in more detail below)may be maintained by the MAC layer 204 of the UE 205.

The eNB 215 can also include a physical (PHY) layer 216, a medium accesscontrol (MAC) layer 218, a radio link control (RLC) layer 220, a packetdata convergence protocol (PDCP) layer 222, and a radio resource control(RRC) layer 224. In case of user plane communication for data traffic,the RRC layer may not be involved. The eNB 215 may also include one ormore antennas 226 coupled to the PHY layer 216. The SRs and ACK/NACKrepetition signals described in this disclosure may be decoded by thephysical layer 216 of the eNB 215. The PUCCH resource for SR, PUCCHresource for ACK/NACK repetition signal, value of SR prohibit timer andthe number of maximum SR transmissions may be configured by the RRClayer 224 of the eNB 215 and be signaled to the UE 205.

Communications between the devices, such as between the eNB 215 and theUE 205, generally occur within the same protocol layer between the twodevices. Thus, for example, communications from the RRC layer 224 at theeNB 215 travel through the PDCP layer 222, the RLC layer 220, the MAClayer 218, and the PHY layer 216, and are sent over the PHY layer 216and the antenna 226 to the UE 205. When received at the antenna 214 ofthe UE 205, the communications travel through the PHY layer 202, the MAClayer 204, the RLC layer 206, the PDCP layer 208 to the RRC layer 210 ofthe UE 205. Such communications are generally done utilizing acommunications sub-system and a processor, as described in more detailbelow.

FIG. 3 is a schematic block diagram 300 illustrating an access nodedevice according to one implementation. The illustrated device 300includes a processing module 302, a wired communication subsystem 304,and a wireless communication subsystem 306. The processing module 302can include one or more processing components (alternatively referred toas “processors” or “central processing units (CPUs)”) capable ofexecuting instructions related to one or more of the processes, steps,or actions described above in connection with one or more of theimplementations disclosed herein. The processing module 302 can alsoinclude other auxiliary components, such as random access memory (RAM),read only memory (ROM), secondary storage (for example, a hard diskdrive or flash memory), etc. The processing module 302 can form at leastpart of the layers described above in connection with FIG. 2. In someimplementations, the processing module 302 may be configured to decodethe received SR and ACK/NACK repetition signal from the UE on a SR PUCCHresource. Further, the processing module 302 may determine that apositive SR from the UE is received in the same subframe as the ACK/NACKrepetition signal when an ACK/NACK repetition signal is detected on theSR PUCCH resource. In some implementations, the processing module 302may be configured not to decode the received SR and ACK/NACK repetitionsignals from the UE in the same subframe. The processing module 302 canexecute certain instructions and commands to provide wireless or wiredcommunication, using the wired communication subsystem 304 or a wirelesscommunication subsystem 306. A skilled artisan may readily appreciatethat various other components can also be included in the device 300.

FIG. 4 is a schematic block diagram 400 illustrating a user equipmentdevice according to one implementation. The illustrated device 400includes a processing unit 402, a computer readable storage medium 404(for example, ROM or flash memory), a wireless communication subsystem406, a user interface 408, and an I/O interface 410.

Similar to the processing module 302 of FIG. 3, the processing unit 402can include one or more processing components (alternatively referred toas “processors” or “central processing units (CPUs)”) configured toexecute instructions related to one or more of the processes, steps, oractions described above in connection with one or more of theimplementations disclosed herein. In some implementations, theprocessing unit 402 may be configured to determine whether a pending SRtransmission may collide with the transmission of an ACK/NACK repetitionsignal, and, responsive to the determining, to refrain from transmittingthe pending SR transmission. Further, the processing unit 402 may beconfigured to refrain from incrementing the SR counter and/or refrainfrom starting the SR prohibit timer, responsive to determining thecollision. In some implementations, the processing unit 402 may beconfigured to determine whether a pending SR transmission may collidewith the transmission of an ACK/NACK repetition signal, and, responsiveto determining the collision, transmit the pending SR and ACK/NACKrepetition signal in the same subframe. The processing unit 402 may alsoinclude other auxiliary components, such as random access memory (RAM)and read only memory (ROM). The computer readable storage medium 404 canstore an operating system (OS) of the device 400 and various othercomputer executable software programs for performing one or more of theprocesses, steps, or actions described above.

The wireless communication subsystem 406 is configured to providewireless communication for data and/or control information provided bythe processing unit 402. The wireless communication subsystem 406 caninclude, for example, one or more antennas, a receiver, a transmitter, alocal oscillator, a mixer, and/or a digital signal processing (DSP)unit. In some implementations, the subsystem 406 can support multipleinput multiple output (MIMO) transmissions.

The user interface 408 can include, for example, one or more of a screenor touch screen (for example, a liquid crystal display (LCD), a lightemitting display (LED), an organic light emitting display (OLED), amicroelectromechanical system (MEMS) display), a keyboard or keypad, atrackball, a speaker, and/or a microphone. The I/O interface 410 caninclude, for example, a universal serial bus (USB) interface. A skilledartisan may readily appreciate that various other components can also beincluded in the device 400.

FIG. 5A is a schematic block diagram 500 illustrating an uplink (UL)hybrid automatic repeat request (HARQ) entity at a user equipmentdevice. As shown in FIG. 5A, an Uplink HARQ Entity 508 maintains anumber of parallel Uplink HARQ Processes 510-514 allowing uplinktransmissions to take place continuously while waiting for the HARQfeedback on the successful or unsuccessful reception of previoustransmissions. A Resource Assignments and ACK/NACK Status Entity 504 mayinform the Uplink HARQ Entity 508 about uplink transmission resourceassignments and received ACK/NACK status from the Physical Layer 202(shown in FIG. 2). The Uplink HARQ Entity 508 may interact with aMultiplexing and Assembly Entity 502 at the UE to obtain a MAC protocoldata unit (PDU) for transmission from the Multiplexing and AssemblyEntity 502. The Uplink HARQ Entity 508 may instruct a Data forTransmission Entity 506 to generate a new transmission, an adaptiveretransmission, or a non-adaptive retransmission after receivingresource assignments, or ACK/NACK notification from the resourceassignments and ACK/NACK Status Entity 504. Although eight uplink HARQprocesses (510, 512, 514) are shown in FIG. 5A, this is illustrativeonly and more or fewer than 8 uplink HARQ processes may be present.

FIG. 5B is a schematic block diagram illustrating the Uplink HARQProcessing Module 510. The illustrated Uplink HARQ Process Module 510includes an Uplink Transmission Buffer 516 and various Uplink HARQParameters 518. The Uplink HARQ Transmission Buffer 516 stores theinformation bits that are to be transmitted and may be more generallyreferred to as an HARQ buffer. The Uplink HARQ Parameters 518 mayinclude various transmission parameters such as transport block size,new data indicator (NDI) flag, modulation and coding scheme (MCS),resource block allocation, frequency hopping parameters, demodulationreference signal (DMRS) cyclic shift, number of transmission attempts,etc.

When a downlink (DL) transport block is received on a physical downlinkshared channel (PDSCH) for a UE, the UE may signal a corresponding ACK(i.e. the PDSCH transport block was successfully decoded) or NACK (i.e.the PDSCH transport block was not successfully decoded) on the uplink.This is normally accomplished in one of two ways. If a PUSCHtransmission is made in the same subframe, then the encoded downlinkACK/NACK information is punctured into that PUSCH transmission. If thereis no PUSCH transmission made in the same subframe, then the downlinkACK/NACK information is signaled via the PUCCH. A UE may be configuredwith ACK/NACK repetition, which may allow, for example, a greaterprobability of correct ACK/NACK detection. ACK/NACK repetition may beconfigured by the eNB. ACK/NACK repetition may be useful, for example,if a UE has a poor transmission channel, or an otherwise challengingchannel condition, between itself and its serving eNB. When the UE isconfigured with ACK/NACK repetition, an ACK/NACK transmitted on theuplink in response to a downlink reception on the PDSCH is repeatedmultiple times, for example, 2, 4, or 6 times (depending upon theconfigured repetition factor) in consecutive uplink subframes. TheACK/NACK signal which is part of an ACK/NACK repetition sequence may betransmitted on an appropriate PUCCH resource.

Collisions may occur when part of the ACK/NACK repetition sequence isconfigured to transmit at the same subframe as a pending schedulingrequest transmission. The UE may transmit a pending scheduling requestto its serving eNB to request uplink resources for uplink datatransmission, e.g., when new uplink traffic arrives at the UE and the UErequires uplink resources for new data transmission. Scheduling requestsare normally transmitted on a PUCCH resource assigned by the eNB. TheeNB may provide configuration information about the PUCCH resources tobe used by a particular UE, and the periodicity and offset within thatperiod specifying when the UE is allowed to use the PUCCH resources.This allows a small number of PUCCH resources to be shared among alarger number of UEs for SR purposes. In some implementations, apresence of SR transmission may imply that the UE is requesting uplinkresources, while an absence of SR transmission may imply that the UE isnot requesting uplink resources. A positive SR may be transmitted viaPUCCH format 1 when the pending SR does not collide with another controlsignal (e.g., an ACK/NACK signal). The PUCCH format 1 communicatesinformation simply by its presence or absence and is thus fairlyreliable even in challenging channel conditions between the UE and theeNB. In addition to the PUCCH resource index, the eNB may also providean SR configuration index for the UE to look up the assigned SRperiodicity and SR subframe offset within that period. For example, SRperiodicities may have values of 1, 2, 5, 10, 20, 40, or 80 subframes(each subframe is 1 ms in length). SR subframe offsets may havenon-negative integer values less than the value of SR periodicity.

When a UE receives downlink transmissions on the PDSCH for which it hasto send an ACK/NACK signal back to the eNB, the same UE may also havepending uplink traffic to transmit which in turn triggers pendingscheduling requests. For example, if the channel conditions between theUE and the eNB are poor, the UE may be configured with ACK/NACKrepetition for greater reception reliability. It is therefore possiblethat the UE may wish to transmit both a pending SR and an ACK/NACKrepetition signal in the same uplink subframe. It is important that boththe SR and the ACK/NACK repetition signal are received at the eNB suchthat the uplink traffic at the UE may be transmitted in a timely fashionvia granting of uplink resources to the UE by the eNB, and that the eNBmay have the knowledge of whether the downlink transmission on PDSCH isreceived successfully at the UE. If an SR is not received at the eNBwithin a certain period of time, the UE may fall back to a random accessprocedure in order to obtain uplink transmission resources, whichtypically causes additional latency. Implementations to handle the SRand ACK/NACK repetition signal collision at the same subframe arepresented in this disclosure to maximize the probability that both theSR and ACK/NACK repetition signal can be received at the eNBsuccessfully within a minimal time of delay.

FIG. 6 is a process flow chart 600 illustrating a method for handling ascheduling request collision with an ACK/NACK repetition signal by a MAClayer at a user equipment device. The illustrated implementation may beapplied to a frequency division duplexing (FDD) or a time divisionduplexing (TDD) wireless communication system. In some implementations,the UE may be configured with only one serving cell and may notcommunicate using carrier aggregation. As shown in FIG. 6, the MAC layerat the UE may check whether a new SR is triggered at step 602. A new SRmay be triggered when new uplink traffic arrives at the UE and no uplinkresource is available for the newly arrived uplink traffic to betransmitted. By way of example, an SR may be triggered when a regularbuffer status report (BSR) has been triggered but cannot be transmittedsince no uplink grant for a new data transmission is available, or ifthe regular BSR was triggered by an event other than new uplink data fora logical channel. If a new SR is triggered at the UE, the UE maycontinue to check whether there is a previous SR pending at step 604. Ifno previous SR is pending, the MAC layer at the UE may set the SRcounter value to 0. The SR counter keeps track of the number oftransmitted SRs. The SR counter may have an integer value in the rangefrom 0 to a maximum SR transmission number, inclusive. In this case,since the SR is newly triggered and no previous SR is pending, the MAClayer at the UE may set the value of SR counter to 0 to start a new SRcounting cycle. If there are previous SRs pending at step 604, the MAClayer at the UE may not reset the SR counter value.

If no new SR is triggered at step 602, if there are previous SRs pendingat step 604, or after the SR counter is set to 0 at step 606, the UEchecks whether there is at least one SR pending at step 608. When a newSR is triggered, it may be considered pending until it is cancelled.Thus, when a new SR is triggered, there may be at least one SR pendingat step 608. If no new SR is triggered and no previous SR is pending,then the condition of at least one SR pending is not satisfied at step608. In this case, the UE may not transmit any SR or execute any ofsteps 610-642, because the UE does not have any pending SR. If there isat least one SR pending at step 608, the UE may to check whether thereare any uplink shared channel (UL-SCH) resources available in thistransmission time interval (TTI), as illustrated at step 610. A TTI maybe equal in length to one subframe. A subframe may be configured to be 1ms in length. The UL-SCH may be an uplink transport channel mappeddirectly to the PUSCH physical channel. If there are UL-SCH resourcesavailable in this TTI, the UE may check whether the new MAC protocoldata unit (PDU) includes BSR information up to and including the lastevent that triggered a BSR or includes all pending data available fortransmission. If the new MAC PDU does include BSR information up to andincluding the last event that triggered a BSR or includes all pendingdata available for transmission, the MAC layer at the UE may cancel allpending SRs and stop the SR prohibit timer at step 616. If the new MACPDU does not include BSR information up to and including the last BSRtrigger at step 612, the UE may check whether the uplink (UL) grant canaccommodate all pending data at step 614. If the UL grant canaccommodate the pending data at step 614, the MAC layer of the UE maycancel the pending SRs and stop the SR prohibit timer at step 616, andskip steps 618-642 regarding to SR transmission. Otherwise, the UE maynot cancel the pending SRs or stop the SR prohibit timer but may skipsteps 618-642 in the process flow diagram.

If there is no UL-SCH resource available in the TTI at step 610, the UEmay check whether a valid PUCCH resource is available for the pending SRtransmission in any TTI at step 618. If no valid PUCCH resource isavailable for the pending SR transmission in any TTI, the UE may cancelthe pending SRs and start a random access procedure at step 620. The UEmay not continue to execute any of steps 622-642 at this point. A randomaccess procedure is an alternative method for the UE to signal to an eNBthat uplink transmission resources are required. The random accessprocedure may be contention-based which typically introduces additionallatency before the UE obtains a useable uplink grant. The UE may consumemore transmission power and cell resources during a random accessprocedure as compared to an SR transmission.

If there is a valid PUCCH resource available for SR transmission in anyTTI, the UE may continue to check whether a valid resource for SRtransmission is available in this TTI at step 622. If no valid PUCCHresource for SR transmission is available in this TTI, the UE may stopthe SR processing for this TTI and skip steps 624-642. Otherwise, the UEmoves on to check whether this TTI is part of a measurement gap at step624. A UE may make measurements of other cells which either are E-UTRAbut which operate on a different frequency band or which belong to adifferent radio access technology (RAT) completely. UEs may only haveone radio for receiving, and hence may tune away this radio from theoperating frequency band of its serving cell in order to makeinter-frequency and/or inter-RAT measurements. In order to facilitatethis, an eNB may configure a UE with measurement gaps, during which theUE is allowed to tune away from the operating frequency band of itsserving cell. Consequently, a UE cannot receive from nor transmit to theserving cell during a configured measurement gap. If a measurement gapoccurs at the time of a pending SR transmission, the SR transmission maynot take place. Therefore, if this TTI is part of a measurement gap atstep 624, the UE may also stop the SR processing for this TTI and skipsteps 626-642.

If this TTI is not part of a measurement gap, the UE checks whether theSR prohibit timer is running at step 626. The SR prohibit timer mayprevent transmission of the pending SRs before the SR prohibit timerexpires. The value of the SR prohibit timer may be configured via theMAC-MainConfig information element. The value of the SR prohibit timermay represent a multiple of the SR periodicity, which may be equal to anSR period multiplied by an integer in the range from 0 to 7, inclusive.If the SR prohibit timer is running at step 626, the UE may not transmitany pending SR or execute any of the steps 628-642. Instead, the SRprocessing for the UE in the TTI may complete if the SR prohibit timeris running. If the SR prohibit timer is not running, the UE may checkwhether the pending SR transmission in this TTI collides with anACK/NACK repetition signal at step 628. The ACK/NACK repetition signalis part of the ACK/NACK repetition sequence, which may comprise theACK/NACK signal repeated 2, 4, or 6 times in consecutive uplinksubframes. If the UE determines that the pending SR transmissioncollides with an ACK/NACK repetition signal in this TTI, the MAC layerat the UE may not transmit the pending SR. Further, the MAC layer at theUE may refrain from incrementing the SR counter, refrain frominstructing the physical layer of the UE to signal the pending SR,and/or refrain from starting the SR prohibit timer. By refraining fromthe incrementing the SR counter and starting the SR prohibit timer, thenumber of opportunities for the UE to transmit a pending SR may not bereduced. By refraining from instructing the physical layer of the UE tosignal the pending SR, the pending SR may not be transmitted in this TTIdue to the collision with the ACK/NACK repetition signal. By refrainingfrom starting the SR prohibit timer, the UE may not have to waitadditional time for the SR prohibit timer to expire before the nextallowable SR transmission opportunity occurs. In other words, the UE maysimply wait until its next SR opportunity to signal an SR when there isa collision between a pending SR transmission and an ACK/NACK repetitionsignal. This may ensure that the UE has the same chance of successfullycompleting a scheduling request procedure without falling back to therandom process procedure, regardless of how many collisions between thepending SR transmission and the ACK/NACK repetition signal occur.

If there is no collision between a pending SR transmission and anACK/NACK repetition signal in this TTI, the UE follows steps 630-642 fora normal SR transmission procedure. The UE may check whether the valueof SR counter is less than the maximum SR transmission number at step630. If the value of the SR counter is equal to or greater than themaximum SR transmission number, the MAC layer of the UE may notify theRRC to release the PUCCH resource for SR and SRS resources at step 638,clear any configured downlink semi-persistent scheduling (SPS) anduplink SPS grants at step 640, cancel all pending SRs and initiate arandom access procedure at 642. The maximum SR transmission number maybe configured by an eNB via the SchedulingRequestConfig informationelement and may have a value of 4, 8, 16, 32, or 64. If the value of theSR counter is less than the maximum SR transmission number, the MAClayer at the UE may increment the value of the SR counter by one at step632, instruct the physical layer to signal SR on PUCCH at step 634, andstart the SR prohibit timer at step 636. Therefore, after the actualtransmission of a pending SR in this TTI, the effective number of SRtransmission opportunities left is reduced by one and the UE may nottransmit another SR before the SR prohibit timer expires.

FIG. 7 is a process flow chart 700 illustrating an alternative methodfor handling a scheduling request collision with an ACK/NACK repetitionsignal by a physical layer at a user equipment device. The illustratedimplementation may be applied to a FDD or a TDD wireless communicationsystem. In some implementations, the UE may be configured with only oneserving cell and may not communicate using carrier aggregation. In theillustrated implementation 700, the pending SR transmission may betransmitted with the ACK/NACK repetition signal in the same TTI even ifthe pending SR transmission collides with the ACK/NACK repetitionsignal. As shown in FIG. 7, the UE first checks whether an ACK/NACKsignal is scheduled for transmission in the current subframe at step702. The ACK/NACK signal may be part of an ACK/NACK repetition sequencewhich comprises the ACK/NACK signal repeated multiple times inconsecutive uplink subframes. If no ACK/NACK signal is scheduled fortransmission in the current subframe, the UE checks whether a pending SRis scheduled for transmission in the current subframe at step 704. Ifthere is a pending SR, the UE may transmit the pending SR on an SR PUCCHresource at step 706. The UE may increment the SR counter by one andstart the SR prohibit timer after transmitting the pending SRtransmission. Otherwise, if there is no SR transmission or ACK/NACKsignal to be transmitted in current subframe at step 704, the UE maystop the SR operation for this subframe at this point.

If an ACK/NACK signal is scheduled for transmission in the currentsubframe at step 702, the UE may check whether a pending SR is alsoscheduled for transmission in the current subframe at step 708. If apending SR is scheduled for transmission with an ACK/NACK signal in thesame subframe, the UE may transmit the ACK/NACK signal on the SR PUCCHresource at step 712. The SR PUCCH resource for the UE may be assignedby the eNB via a RRC message. The UE may increment the SR counter by oneand start the SR prohibit timer after transmitting the pending SRtransmission. The eNB may decode the ACK/NACK signal on SR PUCCHresource. If there is an ACK/NACK signal detected on the SR PUCCHresource, the eNB may consider a positive SR is received. Subsequentlythe eNB may provide uplink resources to the UE by an uplink grant.Otherwise, if no pending SR is scheduled for transmission with theACK/NACK signal, the UE may transmit the ACK/NACK signal on an ACK/NACKPUCCH resource at step 710. The eNB may then decode the ACK/NACK signalon the ACK/NACK PUCCH resource. The PUCCH resource for a first ACK/NACKsignal of an ACK/NACK repetition sequence may be derived from the PDCCHcontrol channel element (CCE) location for a PDSCH reception dynamicallyreceived on the PDCCH. For a downlink SPS reception on the PDSCH, thePUCCH resource for a first ACK/NACK signal of an ACK/NACK repetitionsequence may be configured by the eNB. Subsequent PUCCH resource for theremainder of the ACK/NACK repetition sequence may be semi-staticallyassigned by the eNB as part of the ACK/NACK repetition configuration.Since no SR or ACK/NACK signal is detected on the SR PUCCH resource, theeNB may consider that no SR transmission from the UE is received.

While several implementations have been provided in the presentdisclosure, it should be understood that the disclosed systems andmethods may be embodied in many other specific forms without departingfrom the scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various implementations as discrete or separate maybe combined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

While the above detailed description has shown, described, and pointedout the fundamental novel features of the disclosure as applied tovarious implementations, it may be understood that various omissions andsubstitutions and changes in the form and details of the systemillustrated may be made by those skilled in the art, without departingfrom the intent of the disclosure.

What is claimed is:
 1. A method in a user equipment (UE) comprising:determining that a pending scheduling request (SR) transmission collideswith a transmission of an acknowledgement/negative acknowledgement(ACK/NACK) signal, the ACK/NACK signal being part of an ACK/NACKrepetition sequence; responsive to the determining, refraining fromtransmitting the pending SR transmission; and responsive to thedetermining, refraining from incrementing an SR counter.
 2. The methodof claim 1, further comprising: responsive to the determining,refraining from instructing a physical layer of the UE to signal thepending SR.
 3. The method of claim 1, further comprising: responsive tothe determining, refraining from starting an SR prohibit timer.
 4. Themethod of claim 3, wherein the SR prohibit timer has a value equal to anSR period multiplied by an integer in a range from 0 to 7, inclusive. 5.The method of claim 1, further comprising transmitting a subsequent SRtransmission.
 6. The method of claim 5, wherein the subsequent SRtransmission is transmitted on a physical uplink control channel(PUCCH).
 7. The method of claim 1, further comprising determining that aPUCCH resource is available for the pending SR transmission prior todetermining that the pending SR transmission collides with the ACK/NACKsignal.
 8. The method of claim 1, wherein the ACK/NACK signal istransmitted on an uplink in response to a physical downlink sharedchannel (PDSCH) reception.
 9. The method of claim 1, wherein theACK/NACK repetition sequence comprises the ACK/NACK signal repeated 2,4, or 6 times in consecutive uplink subframes.
 10. The method of claim1, wherein the SR counter has an integer value in a range from 0 to amaximum SR transmission number, inclusive.
 11. A method in a userequipment (UE) comprising: determining that a pending scheduling request(SR) transmission collides with a transmission of anacknowledgement/negative acknowledgement (ACK/NACK) signal, wherein theACK/NACK signal is a part of an ACK/NACK repetition sequence;transmitting the pending SR transmission and the ACK/NACK signal in thesame subframe.
 12. The method of claim 11, wherein the ACK/NACK signalis transmitted on an uplink in response to a physical downlink sharedchannel (PDSCH) reception.
 13. The method of claim 11, wherein theACK/NACK repetition sequence comprises the ACK/NACK signal repeated 2,4, or 6 times in consecutive uplink subframes.
 14. The method of claim11, wherein an SR PUCCH resource is used by the UE to transmit theACK/NACK signal.
 15. The method of claim 11, further comprisingincrementing an SR counter by one.
 16. The method of claim 15, whereinthe SR counter has an integer value in a range from 0 to a maximum SRtransmission number, inclusive.
 17. The method of claim 11, furthercomprising instructing a physical layer of the UE to signal SR on PUCCH.18. The method of claim 11, further comprising starting an SR prohibittimer.
 19. The method of claim 18, wherein the SR prohibit timer has avalue equal to an SR period multiplied by an integer in a range from 0to 7, inclusive.
 20. The method of claim 11, wherein the UE operates ina frequency division duplexing (FDD) mode or in a time divisionduplexing (TDD) mode.